simplex

BASICS


DESCRIPTION


• Herpes simplex virus type 1 causes ocular infection following introduction of the virus in childhood as a subclinical or mild systemic infection. The HSV becomes latent in ganglion around the eye (trigeminal). The virus or viral genome may remain latent for decades before reactivating to cause various forms of herpetic keratitis.


• Conjunctival inflammation precedes corneal vesicles, Superficial Punctate Keratitis (SPK), and then branching epithelial ulcer, a classic dendritic ulcer which may enlarge to a geographic form.


• Deeper corneal forms of herpes simplex virus keratitis (HSVK) may follow days/weeks later. Disciform keratitis is an immune form of HSV involving corneal endothelium leading to edema. With persistence, corneal scarring, thinning, and rarely, perforation.


EPIDEMIOLOGY


Incidence


• HSV type 1 is the leading cause of blindness from an infectious corneal disease. By age 5 years, over 60% show antibody evidence systemic HSV.


• About 1% of HSV infected patients develop ocular HSV.


Prevalence


• There are about 20,000 new primary cases of HSVK seen yearly. Most are dendritic keratitis.


• About 30,000 recurrent HSVK cases are seen annually.


RISK FACTORS


Fever, URI, ocular trauma, menses, high stress, CL use, all have been considered risk factors, but not proven.


Genetics


Probably exist but not defined.


GENERAL PREVENTION


Oral antivirals are useful to prevent recurrent HSVK. Most helpful with previous hx of multiple recurrences of HSVK.


PATHOPHYSIOLOGY


Systemic viremia of HSV early in life seeds ganglia around the eye. Later reactivation of latent virus causes infection.


COMMONLY ASSOCIATED CONDITIONS


Fever blisters around the mouth, nose, and eye often accompany ocular HSV.


DIAGNOSIS


HISTORY


Ocular inflammation and eye irritation (pain) often precede HSVK. Blurred VA when the infection is in the visual axis.


PHYSICAL EXAM


Slit-lamp examination is critical to diagnose ocular HSV. Vital dyes such as fluorescein, lissamine green, or Bengal rose are very helpful.


DIAGNOSTIC TESTS & INTERPRETATION


Lab


Most often lab tests such as culture are not necessary as slit-lamp diagnosis of dendritic keratitis is very specific. With more complicated, deeper forms of HSVK, culture, PCR, or immune tests are used.


Imaging


None.


Pathological Findings


Pathological studies are rarely performed.


DIFFERENTIAL DIAGNOSIS


Can be confused with herpes zoster keratitis, Epstein Barr, acanthamoeba, fungal keratitis, and other persistent unusual deeper corneal infections.


TREATMENT


MEDICATION


First Line


Dendritic keratitis responds well to trifluridine drops topically and third generation topical gels such as ganciclovir. Oral antivirals, acyclovir and valacyclovir are useful. Steroids should be avoided for ocular surface HSVK, but are used with antivirals for stromal HSVK, disciform, necrotizing and uveitis.


SURGERY/OTHER PROCEDURES


Penetrating keratoplasty for severe stromal scarring, thinning, or perforation is helpful.


ONGOING CARE


FOLLOW-UP RECOMMENDATIONS


Patient Monitoring


With HSV dendritic keratitis follow-up, slit-lamp exams as necessary until resolution, with stromal disease, very long term follow-up is critical. Herpes is forever.


PATIENT EDUCATION


Discussion of long-term therapy. Not to self-medicate with recurrences, but to expedite office examination.


PROGNOSIS


Good for initial and early recurrent dendritic keratitis with topical Rx. Or oral Rx. Guarded for stromal HSV.


COMPLICATIONS


Significant morbidity and visual loss with stromal HSV.


Pediatric Considerations


Infants and children can develop HSVK after loss of maternal antibodies. Steroids should never be used for a red eye in this group unless a slit-lamp examination is done.


ADDITIONAL READING


• Young RC, Hodge DO, Liesegang TJ, et al. Incidence, recurrence, and outcomes of herpes simplex virus eye disease in Olmsted County, Minnesota, 1976–2007: The effect of oral antiviral prophylaxis. Arch Ophthalmol 2010;128(9):1178–1183.


• Knickelbein JE, Hendricks RL, Charukamnoetkanok P. Management of hsv stromal keratitis: An evidence-based review. Surv Ophthal 2009; 54(2):226–234.


CODES


ICD9


054.42 Dendritic keratitis


054.43 Herpes simplex disciform keratitis


CLINICAL PEARLS


• Always suspect possible ocular HSV in patients. With acute red eye and do slit-lamp examination with vital dye to avoid treating HSV with topical steroids especially in children.


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Nov 9, 2016 | Posted by in OPHTHALMOLOGY | Comments Off on simplex

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